The objective of this research is to determine whether microbial calcification can provide a model system for vertebrate calcification. Bacterionema matruchotii, an actinomycete of the human oral biota, forms intracellular apatite crystallographically indistinguishable from bone mineral. Proteolipid has been identified as the nucleator of B. matruchotii calcification. Calcifiable proteolipids have also been isolated from human dental calculus and marmoset bone. Both B. matruchotii and bone proteolipids are composed of basic, hydrophobic protein complexed with acidic phospholipids. B. matruchotii Richardson Strin 13, which have been treated with acridine organge (A013) exhibit impaired calcifiability. By comparing Strain 13 and A013 this research seeks to elucidate the mechanism of intracellular calcium phosphate deposition. Studies will include determination of possible alterations in cellular metabolism responsible for impairment of calcifiability as well as a comparison of the nucleator. Techniques developed for the characterization of the bacterial proteolipid will be applied to normal and pathologic vertebrate calcifications. BIBLIOGRAPHIC REFERENCES: Vogel, James J. and Boyan-Salyers, Barbara: Acidic lipids associated with the local mechanism of calcification. A review. Clin. Orthop. & Rel. Res. 118: 230-241, 1976. Ennever, John, Vogel, J.J., Rider, L.J. and Boyan-Salyers, B.: Nucleation of microbiologic calcification by proteolipid. Proc. Soc. Exp. Biol. Med. 152: 147-150, 1976.